Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast . Lactic acid from fermentation imparts a sour taste and improves keeping-qualities.
99-582: In the Encyclopedia of Food Microbiology , Michael Gaenzle writes: "One of the oldest sourdough breads dates from 3700 BCE and was excavated in Switzerland, but the origin of sourdough fermentation likely relates to the origin of agriculture in the Fertile Crescent and Egypt several thousand years earlier", and "Bread production relied on the use of sourdough as a leavening agent for most of human history;
198-472: A bread that is crunchy outside but soft and savory inside. Amish friendship bread uses a sourdough starter that includes sugar and milk . It is also leavened with baking powder and baking soda. An Amish sourdough is fed with sugar and potato flakes every 3–5 days. German pumpernickel is traditionally made from a sourdough starter, although modern pumpernickel loaves often use commercial yeasts, sometimes spiked with citric acid or lactic acid to inactivate
297-413: A class of compounds that are "structurally and metabolically" related to sucrose , where "carbon is stored as sucrose and polymers of fructose ( fructans )." Yeasts have the ability to free fructose from glucofructans which compose about 1–2% of the dough. Glucofructans are long strings of fructose molecules attached to a single glucose molecule. Sucrose can be considered the shortest glucofructan, with only
396-403: A denser finished product. As it ferments, sometimes for several days, the volume of the starter is increased by periodic additions of flour and water, called "refreshments" or referred to as a "feeding". As long as this starter culture is fed flour and water regularly, it will remain active. The ratio of fermented starter to fresh flour and water is critical in the development and maintenance of
495-485: A dough's glutathione increases elasticity. Common oxidizing agents are: Reducing agents help to weaken the flour by breaking the protein network. This will help with various aspects of handling a strong dough. The benefits of adding these agents are reduced mixing time, reduced dough elasticity, reduced proofing time, and improved machinability. Cysteine and bisulfite are reducing agents which relax wheat dough. Adding minute amounts of oxidants or reducing agents alter
594-623: A laboratory environment provides insight into the three-phase evolution of first-generation-to-stable sourdough ecosystems. In the first two days of refreshment, atypical genera Enterococcus and Lactococcus bacteria highlighted the doughs. During days 2–5, sourdough-specific bacteria belonging to the genera Lactobacillus , Pediococcus , and Weissella outcompete earlier strains. Yeasts grew more slowly and reached population peaks near days 4–5. By days 5–7, "well-adapted" Lactobacillus strains such as L. fermentum and Lactiplantibacillus plantarum had emerged. At their peaks, yeast populations were in
693-400: A large scale in the 1980s and 1990s as a fuel additive to gasoline, due to government regulations. Today, ethanol continues to be explored as a sustainable and renewable fuel source, with researchers developing new technologies and biomass sources for its production. Homolactic fermentation (producing only lactic acid) is the simplest type of fermentation. Pyruvate from glycolysis undergoes
792-650: A mixture of flour and water . Broadly speaking, the yeast produces gas ( carbon dioxide ) which leavens the dough, and the lactic acid bacteria produce lactic acid, which contributes flavor in the form of sourness. The lactic acid bacteria metabolize sugars that the yeast cannot, while the yeast metabolizes the by-products of lactic acid fermentation . During sourdough fermentation, many cereal enzymes, particularly phytases, proteases and pentosanases, are activated through acidification and contribute to biochemical changes during sourdough fermentation. Every starter consists of different lactic acid bacteria which are introduced to
891-533: A new starter every time they bake. The original starter culture may be many years old. Because of their pH level and the presence of antibacterial agents, such cultures are stable and able to prevent colonization by unwanted yeasts and bacteria. For this reason, sourdough products inherently keep fresh for a longer time than other breads, and are good at resisting spoilage and mold without the additives required to retard spoiling of other types of bread. The flavour of sourdough bread varies from place to place according to
990-493: A pH less than 3.5, and are fermented within a temperature range of 30 to 50 °C (86 to 122 °F) for several days without feedings, which reduces the flora's activity. This process was adopted by some in industry, in part, due to simplification of the multiple-step build typical of Type I sourdoughs. In Type II sourdoughs, yeast growth is slowed or stopped due to higher fermentation temperatures. These doughs are more liquid and once fermented may be chilled and stored for up to
1089-776: A pH range of 3.8 to 4.5, and are fermented in a temperature range of 20 to 30 °C (68 to 86 °F). Fructilactobacillus sanfranciscensis was named for its discovery in San Francisco sourdough starters, though it is not endemic to San Francisco. F. sanfranciscensis and Limosilactobacillus pontis often highlight a lactic-acid bacterial flora that includes Limosilactobacillus fermentum , Fructilactobacillus fructivorans , Levilactobacillus brevis , and Companilactobacillus paralimentarius . The yeasts Saccharomyces exiguus , Kasachstania humilis , or Candida holmii usually populate sourdough cultures symbiotically with Fructilactobacillus sanfranciscensis . The perfect yeast S. exiguus
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#17328560747731188-662: A process formerly thought to be merely a chemical change. His work in identifying the role of microorganisms in food spoilage led to the process of pasteurization . In 1877, working to improve the French brewing industry , Pasteur published his famous paper on fermentation, " Etudes sur la Bière ", which was translated into English in 1879 as "Studies on fermentation". He defined fermentation (incorrectly) as "Life without air", yet he correctly showed how specific types of microorganisms cause specific types of fermentations and specific end-products. Although showing fermentation resulted from
1287-643: A pronounced sourness, and indeed the strain of Lactobacillus in sourdough starters is named Fructilactobacillus sanfranciscensis (previously Lactobacillus sanfranciscensis ), alongside the sourdough yeast Kasachstania humilis (previously Candida milleri ) found in the same cultures. The sourdough tradition was carried into the Department of Alaska in the United States and the Yukon Territory in Canada during
1386-585: A redox cofactor , which in turn transfers them to an organic compound. ATP is generated in the process, and it can be formed by substrate-level phosphorylation or by ATP synthase. When glucose is fermented, it enters glycolysis or the pentose phosphate pathway and is converted to pyruvate. From pyruvate, pathways branch out to form a number of end products (e.g. lactate). At several points, electrons are released and accepted by redox cofactors ( NAD and ferredoxin ). At later points, these cofactors donate electrons to their final acceptor and become oxidized. ATP
1485-468: A relatively low glycemic index compared with other types of bread. The activity of cereal enzymes during sourdough fermentation hydrolyses phytates , which improves the absorption of some dietary minerals and vitamins, most of which are found in the bran. Sourdough fermentation reduces wheat components that may contribute to non-celiac wheat sensitivity and irritable bowel syndrome . Sourdough fermentation and lactic acid bacteria may be useful to improve
1584-469: A religious significance in Judaism and Christianity . The Baltic god Rugutis was worshiped as the agent of fermentation. In alchemy , fermentation ("putrefaction") was symbolized by Capricorn [REDACTED] ♑︎ . In 1837, Charles Cagniard de la Tour , Theodor Schwann and Friedrich Traugott Kützing independently published papers concluding, as a result of microscopic investigations, that yeast
1683-733: A salted wheat-rye dough takes about 54 hours at 27 °C (81 °F) to stabilise at a pH between 4.4 and 4.6. 4% salt inhibits L. sanfranciscensis , while C. milleri can withstand 8%. A drier and cooler starter has less bacterial activity and more yeast growth, which results in the bacterial production of more acetic acid relative to lactic acid. Conversely, a wetter and warmer starter has more bacterial activity and less yeast growth, with more lactic acid relative to acetic acid. The yeasts produce mainly CO 2 and ethanol. High amounts of lactic acid are desired in rye and mixed-rye fermentations, while relatively higher amounts of acetic acid are desired in wheat fermentations. A dry, cool starter produces
1782-530: A simple redox reaction, forming lactic acid . Overall, one molecule of glucose (or any six-carbon sugar) is converted to two molecules of lactic acid: It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some kinds of bacteria (such as lactobacilli ) and some fungi . It is the type of bacteria that convert lactose into lactic acid in yogurt , giving it its sour taste. These lactic acid bacteria can carry out either homolactic fermentation , where
1881-446: A single fructose molecule attached. When L. sanfrancisensis reduces all available fructose, it stops producing acetic acid and begins producing ethanol. If the fermenting dough gets too warm, the yeasts slow down, producing less fructose. Fructose depletion is more of a concern in doughs with lower enzymatic activities. A Belgian study of wheat and spelt doughs refreshed once every 24 hours and fermented at 30 °C (86 °F) in
1980-514: A sourer loaf than a wet, warm one. Firm starters (such as the Flemish Desem starter, which may be buried in a large container of flour to prevent drying out) tend to be more resource-intensive than wet ones. A stable culture in which F. sanfranciscensis is the dominant bacterium requires a temperature between 25–30 °C (77–86 °F) and refreshments every 24 hours for about two weeks. Refreshment intervals of longer than three days acidify
2079-479: A starter. This ratio is called the refreshment ratio . Higher refreshment ratios are associated with greater microbial stability in the sourdough. In San Francisco sourdough, the ratio is 40% of the total weight, which is roughly equivalent to 67% of the new-dough's weight. A high refreshment ratio keeps acidity of the refreshed dough relatively low. Acidity levels of below pH 4.0 inhibit lactobacilli and favor acid-tolerant yeasts. A starter prepared from scratch with
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#17328560747732178-532: A stationary phase after most of the nutrients have been consumed, and then the cells die. Fed-batch fermentation is a variation of batch fermentation where some of the ingredients are added during the fermentation. This allows greater control over the stages of the process. In particular, production of secondary metabolites can be increased by adding a limited quantity of nutrients during the non-exponential growth phase. Fed-batch operations are often sandwiched between batch operations. The high cost of sterilizing
2277-850: A steady state and avoid contamination, and the design tends to be complex. Typically the fermentor must run for over 500 hours to be more economical than batch processors. The use of fermentation, particularly for beverages , has existed since the Neolithic and has been documented dating from 7000 to 6600 BCE in Jiahu , China , 5000 BCE in India , Ayurveda mentions many Medicated Wines, 6000 BCE in Georgia, 3150 BCE in ancient Egypt , 3000 BCE in Babylon , 2000 BCE in pre-Hispanic Mexico, and 1500 BC in Sudan . Fermented foods have
2376-580: A sugar solution, forming carbon dioxide and alcohol much like living yeasts. Buechner's results are considered to mark the birth of biochemistry. The "unorganized ferments" behaved just like the organized ones. From that time on, the term enzyme came to be applied to all ferments. It was then understood fermentation is caused by enzymes produced by microorganisms. In 1907, Buechner won the Nobel Prize in chemistry for his work. Advances in microbiology and fermentation technology have continued steadily up until
2475-594: A temperature of 70 °C. This is just below its boiling point (78 °C), making it easy to extract. Halophilic bacteria can produce bioplastics in hypersaline conditions. Solid-state fermentation adds a small amount of water to a solid substrate; it is widely used in the food industry to produce flavors, enzymes and organic acids. In continuous fermentation, substrates are added and final products removed continuously. There are three varieties: chemostats , which hold nutrient levels constant; turbidostats , which keep cell mass constant; and plug flow reactors in which
2574-414: A term that is still applied to any Alaskan or Klondike old-timer. The significance of the nickname's association with Yukon culture was immortalized in the writings of Robert Service , particularly his collection of " Songs of a Sourdough ". In English-speaking countries, where wheat-based breads predominate, sourdough is no longer the standard method for bread leavening. It was gradually replaced, first by
2673-421: A time, or simply by leaving it uncovered for at least 24 hours. Chlorine and chloramines can both be removed by activated carbon filters . Adding a small quantity of diastatic malt provides maltase and simple sugars to support the yeasts initially. Bakers often make loaves with fermented dough from a previous batch (which they call "mother dough", "mother sponge", "chef", or "seed sour") rather than making
2772-798: A vat instead of meat. Industrial fermentation can be used for enzyme production, where proteins with catalytic activity are produced and secreted by microorganisms. The development of fermentation processes, microbial strain engineering and recombinant gene technologies has enabled the commercialization of a wide range of enzymes. Enzymes are used in all kinds of industrial segments, such as food (lactose removal, cheese flavor), beverage (juice treatment), baking (bread softness, dough conditioning), animal feed, detergents (protein, starch and lipid stain removal), textile, personal care and pulp and paper industries. Most industrial fermentation uses batch or fed-batch procedures, although continuous fermentation can be more economical if various challenges, particularly
2871-525: A week. They are pumpable and used in continuous bread production systems. Type III sourdoughs are Type II sourdoughs subjected to a drying process, usually either spray or drum drying , and are mainly used at an industrial level as flavoring agents. They are dominated by "drying-resistant [lactic acid bacteria] such as Pediococcus pentosaceus , L. plantarum , and L. brevis ." The drying conditions, time and heat applied, may be varied in order to influence caramelization and produce desired characteristics in
2970-418: A wide range of consumer goods, from food and drink to industrial chemicals and pharmaceuticals. Since its early beginnings in ancient civilizations, the use of fermentation has continued to evolve and expand, with new techniques and technologies driving advances in product quality, yield, and efficiency. The period from the 1930s onward saw a number of significant advancements in fermentation technology, including
3069-439: Is a substrate for methanogens and sulfate reducers , which keep the concentration of hydrogen low and favor the production of such an energy-rich compound, but hydrogen gas at a fairly high concentration can nevertheless be formed, as in flatus . For example, Clostridium pasteurianum ferments glucose to butyrate , acetate , carbon dioxide, and hydrogen gas: The reaction leading to acetate is: Glyoxylate fermentation
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3168-400: Is a living organism that reproduces by budding . Schwann boiled grape juice to kill the yeast and found that no fermentation would occur until new yeast was added. However, a lot of chemists, including Antoine Lavoisier , continued to view fermentation as a simple chemical reaction and rejected the notion that living organisms could be involved. This was seen as a reversion to vitalism and
3267-635: Is a part of the appeal. As described by one enthusiast, "If you take flour, water, (wild) yeast and salt, and play around with time and temperature, what comes out of the oven is something utterly transformed." Many bakers feed their starters on elaborate schedules, and many name them. Some approach sourdough as science, attempting to optimize flavor and acidity with careful measurements, experimentation, and correspondence with professional microbiologists. Some lineages of starter are freely shared, and others can be purchased, but many prefer to cultivate their own. Some techniques for doing so are fiercely debated, such as
3366-465: Is a type of fermentation used by microbes that are able to utilize glyoxylate as a nitrogen source. Other types of fermentation include mixed acid fermentation , butanediol fermentation , butyrate fermentation , caproate fermentation , and acetone–butanol–ethanol fermentation . In food and industrial contexts, any chemical modification performed by a living being in a controlled container can be termed "fermentation". The following do not fall into
3465-548: Is achieved in bakeries that use sourdough as sole leavening agents but not by amateur bakers that use the sourdough only weekly or even less frequently. Bakers have devised several ways of encouraging a stable culture of micro-organisms in the starter. Unbleached , unbromated flour contains more micro-organisms than more processed flours. Bran -containing (wholemeal) flour provides the greatest variety of organisms and additional minerals, though some cultures use an initial mixture of white flour and rye or whole wheat flour or "seed"
3564-458: Is also formed at several points in the pathway. While fermentation is simple in overview, its details are more complex. Across organisms, fermentation of glucose involves over 120 different biochemical reactions. Further, multiple pathways can be responsible for forming the same product. For forming acetate from its immediate precursor (pyruvate or acetyl-CoA), six separate pathways have been found. In ethanol fermentation, one glucose molecule
3663-501: Is converted into two ethanol molecules and two carbon dioxide (CO 2 ) molecules. It is used to make bread dough rise: the carbon dioxide forms bubbles, expanding the dough into a foam. The ethanol is the intoxicating agent in alcoholic beverages such as wine, beer and liquor. Fermentation of feedstocks, including sugarcane , maize , and sugar beets , produces ethanol that is added to gasoline . In some species of fish, including goldfish and carp , it provides energy when oxygen
3762-403: Is in a sense intermediate between lactic acid fermentation and other types, e.g. alcoholic fermentation . Reasons to go further and convert lactic acid into something else include: Hydrogen gas is produced in many types of fermentation as a way to regenerate NAD from NADH. Electrons are transferred to ferredoxin , which in turn is oxidized by hydrogenase , producing H 2 . Hydrogen gas
3861-461: Is known to survive without oxygen. Fermentation uses a range of substrates and forms a variety of metabolic end products. Of the 55 end products formed, the most common are acetate and lactate. Of the 46 chemically-defined substrates that have been reported, the most common are glucose and other sugars. When an organic compound is fermented, it is broken down to a simpler molecule and releases electrons. The electrons are transferred to
3960-460: Is leavened using baker's yeast or chemical raising agents as well as, or instead of, a live sourdough starter culture. The Real Bread Campaign calls these products sourfaux. Manufacturers of non-sourdough breads make up for the lack of yeast and bacterial culture by introducing into their dough an artificially made mix known as bread improver or flour improver. Sourdough baking has a devoted community today. Many devotees share starters and tips via
4059-453: Is longer than that of breads made with baker's yeasts, sourdough starters are generally unsuitable for use in a bread machine . However, sourdough that has been proofed over many hours, using a sourdough starter or mother dough , can then be transferred to the machine, utilizing only the baking segment of the bread-making program, bypassing timed mechanical kneading by the machine's paddle. This may be convenient for single loaf production, but
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4158-409: Is made from microorganisms carefully isolated from Petri dishes , grown into large, homogeneous populations in fermentors, and processed into combined baker's products with numerically defined ratios and known quantities of microorganisms well suited to particular bread styles. Maintaining metabolically active sourdough with high leavening activity typically requires several refreshments per day, which
4257-498: Is most common in the phylum Bacillota , and it is least common in Actinomycetota . Their most common habitat is host-associated ones, such as the gut. Animals, including humans, also carry out fermentation. The product of fermentation in humans is lactate, and it is formed during anaerobic exercise or in cancerous cells . No animal is known to survive on fermentation alone, even as one parasitic animal ( Henneguya zschokkei )
4356-457: Is not required, it is an alternative to aerobic respiration . Over 25% of bacteria and archaea carry out fermentation. They live in the gut , sediments , food , and other environments. Eukaryotes, including humans and other animals, also carry out fermentation. Fermentation is important in several areas of human society. Humans have used fermentation in production of food for 13,000 years. Humans and their livestock have microbes in
4455-489: Is often addition of small quantities of chemicals to control the pH or suppress foaming. Batch fermentation goes through a series of phases. There is a lag phase in which cells adjust to their environment; then a phase in which exponential growth occurs. Once many of the nutrients have been consumed, the growth slows and becomes non-exponential, but production of secondary metabolites (including commercially important antibiotics and enzymes) accelerates. This continues through
4554-441: Is ready to use when it is bubbly and floats in water. The leaven is mixed with flour and water to make a final dough of the desired consistency. The starter weight is usually 13% to 25% of the total flour weight, though formulas may vary. Using a smaller ratio of cold un-feed starter in the range of 5% to 10% can also create good sourdough loaves, however, the fermentation time will be longer and can result in improved flavor. The dough
4653-491: Is reduced into ethanol using the energy and hydrogen from NADH, and the NADH is oxidized into NAD so that the cycle may repeat. The reaction is catalyzed by the enzymes pyruvate decarboxylase and alcohol dehydrogenase. The history of ethanol as a fuel spans several centuries and is marked by a series of significant milestones. Samuel Morey , an American inventor, was the first to produce ethanol by fermenting corn in 1826. However, it
4752-419: Is related to the imperfect yeasts C. milleri and C. holmii . Torulopsis holmii , Torula holmii , and S. rosei are synonyms used prior to 1978. C. milleri and C. holmii are physiologically similar, but DNA testing established them as distinct. Other yeasts reported found include C. humilis , C. krusei , Pichia anomaola , C. peliculosa , P. membranifaciens , and C. valida . There have been changes in
4851-426: Is scarce (along with lactic acid fermentation). Before fermentation, a glucose molecule breaks down into two pyruvate molecules ( glycolysis ). The energy from this exothermic reaction is used to bind inorganic phosphates to ADP, which converts it to ATP, and convert NAD to NADH. The pyruvates break down into two acetaldehyde molecules and give off two carbon dioxide molecules as waste products. The acetaldehyde
4950-434: Is shaped into loaves, left to rise, and then baked. A number of 'no knead' methods are available for sourdough bread. Due to the length of time sourdough bread takes to proof, many bakers may refrigerate their loaves prior to baking. This process is known as 'retardation' to slow down the proofing process. This process has the added benefit of developing a richer flavoured bread. Because the rise time of most sourdough starters
5049-402: Is to produce a vigorous leaven and to develop the flavour of the bread. In practice there are several kinds of starters, as the ratio of water to flour in the starter ( hydration ) varies. A starter may be a liquid batter or a stiff dough. Flour naturally contains a variety of yeasts and bacteria. When wheat flour comes into contact with water, the naturally occurring enzyme amylase breaks down
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#17328560747735148-465: Is treated by chlorination or chloramination , adding small amounts of substances that inhibit potentially dangerous micro-organisms but are harmless to animals. Some bakers recommend unchlorinated water for feeding cultures. Because a sourdough fermentation relies on microorganisms, using water without these agents may produce better results. Bottled drinking water is suitable; chlorine, but not chloramines , can be removed from tap water by boiling it for
5247-468: Is used as a yeast stimulant. Calcium iodate, an oxidant, is a U.S. Food and Drug Administration generally recognized as safe source of calcium. Oxidizing agents are added to flour to help with gluten development. They may or may not also act as bleaching agents. Originally flour was naturally aged through exposure to the atmosphere. Oxidizing agents primarily affect sulfur-containing amino acids, ultimately helping to form disulfide bridges between
5346-518: The California Gold Rush , and it remains a part of the culture of San Francisco today. (The nickname remains in " Sourdough Sam ", the mascot of the San Francisco 49ers .) Sourdough has long been associated with the 1849 gold prospectors, though they were more likely to make bread with commercial yeast or baking soda. The "celebrated" San Francisco sourdough is a white bread characterized by
5445-538: The Internet . Hobbyists often share their work on social media . Sourdough cultures contain communities of living organisms, with a history unique to each individual starter, and bakers can feel an obligation to maintain them. The different yeasts present in the air in any region also enter sourdough, causing starters to change depending on location. Some devotees find interest in history. Sourdough expert Ed Wood isolated millennia-old yeast from an ancient Egyptian bakery near
5544-497: The Klondike Gold Rush of 1898. Conventional leavenings such as yeast and baking soda were much less reliable in the conditions faced by the prospectors. Experienced miners and other settlers frequently carried a pouch of starter either around their neck or on a belt; these were fiercely guarded to keep from freezing. However, freezing does not kill a sourdough starter; excessive heat does. Old hands came to be called "sourdoughs",
5643-725: The pyramids of Giza , and many individual starters, such as Carl Griffith's 1847 starter , have been passed down through generations. "I like the throwback of traditional bread, the things our great grandmothers ate," writes professional baker Stacie Kearney. Some bakers describe starters generations old, though Griffith's seems exceptional. Sourdough baking became more popular during the COVID-19 pandemic , as increased interest in home baking caused shortages of baker's yeast in stores, whereas sourdough can be propagated at home. Sourdough baking requires minimal equipment and simple ingredients – flour, salt, and water – but invites practice. Purism
5742-435: The starch into the sugars glucose and maltose , which sourdough's natural yeast can metabolize. With sufficient time, temperature, and refreshments with new or fresh dough, the mixture develops a stable culture. This culture will cause a dough to rise. The bacteria ferment starches that the yeast cannot metabolise, and the by-products, chiefly maltose, are metabolised by the yeast, which produces carbon dioxide gas, leavening
5841-623: The taxonomy of yeasts in recent decades. F. sanfranciscensis requires maltose, while C. milleri is maltase negative and thus cannot consume maltose. C. milleri can grow under conditions of low pH and relatively high acetate levels, a factor contributing to sourdough flora's stability. In order to produce acetic acid, F. sanfrancisensis needs maltose and fructose . Wheat dough contains abundant starch and some polyfructosanes , which enzymes degrade to "maltose, fructose and little glucose ." The terms "fructosan, glucofructan, sucrosyl fructan, polyfructan, and polyfructosan" are all used to describe
5940-450: The 20th century, sourdough became less common, replaced by the faster-acting baker’s yeast. Sometimes, this yeast is supplemented with longer fermentation periods to allow some bacterial activity, which adds flavor. During the 2010s, sourdough fermentation regained popularity as a major method in bread production, often used alongside baker’s yeast as a leavening agent. French bakers brought sourdough techniques to Northern California during
6039-527: The action of living microorganisms was a breakthrough, it did not explain the basic nature of fermentation; nor did it prove it is caused by microorganisms which appear to be always present. Many scientists, including Pasteur, had unsuccessfully attempted to extract the fermentation enzyme from yeast . Success came in 1897 when the German chemist Eduard Buechner ground up yeast, extracted a juice from them, then found to his amazement this "dead" liquid would ferment
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#17328560747736138-549: The amylases in the rye flour. Flemish desem bread (the word means 'starter') is a whole-wheat sourdough. Whole-wheat sourdough flatbreads are traditionally eaten in Azerbaijan. In Ethiopia, teff flour is fermented to make injera . A similar variant is eaten in Somalia, Djibouti, and Yemen (where it is known as lahoh ). In India, idlis and dosa are made from a sourdough fermentation of rice and Vigna mungo . Sourdough bread has
6237-470: The baked product. There are many breads that use techniques similar to that used in the making of sourdough bread. Danish rugbrød ( rye bread ) is a dense, dark bread best known from its use in the Danish smørrebrød (open-faced sandwiches). The Mexican birote salado started out in the city of Guadalajara as a short French baguette that replaces the yeast with a sourdough fermentation process, yielding
6336-692: The biochemical sense, but are called fermentation in the larger sense: Fermentation can be used to make alternative protein sources. It is commonly used to modify existing protein foods, including plant-based ones such as soy, into more flavorful forms such as tempeh and fermented tofu . More modern "fermentation" makes recombinant protein to help produce meat analogue , milk substitute , cheese analogues , and egg substitutes . Some examples are: Heme proteins such as myoglobin and hemoglobin give meat its characteristic texture, flavor, color, and aroma. The myoglobin and leghemoglobin ingredients can be used to replicate this property, despite them coming from
6435-415: The complex blistered and slashed crust characteristics of oven-baked sourdough bread cannot be achieved in a bread making machine, as this usually requires the use of a baking stone in the oven and misting of the dough to produce steam. Furthermore, ideal crust development requires loaves of shapes not achievable in a machine's loaf tin. Sourdough is a stable culture of lactic acid bacteria and yeast in
6534-405: The culture medium flows steadily through a tube while the cells are recycled from the outlet to the inlet. If the process works well, there is a steady flow of feed and effluent and the costs of repeatedly setting up a batch are avoided. Also, it can prolong the exponential growth phase and avoid byproducts that inhibit the reactions by continuously removing them. However, it is difficult to maintain
6633-449: The culture using unwashed organic grapes (for the wild yeasts on their skins). Grapes and grape must are also sources of lactic acid bacteria, as are many other edible plants. Basil leaves are soaked in room-temperature water for an hour to seed traditional Greek sourdough. Using water from boiled potatoes is said to increase the activity of the bacteria by providing additional starch. The piped drinking water supplied in most urban areas
6732-494: The development of new processes for producing high-value products like antibiotics and enzymes, the increasing importance of fermentation in the production of bulk chemicals, and a growing interest in the use of fermentation for the production of functional foods and nutraceuticals. The 1950s and 1960s saw the development of new fermentation technologies, such as the use of immobilized cells and enzymes, which allowed for more precise control over fermentation processes and increased
6831-473: The difficulty of maintaining sterility, can be met. In a batch process, all the ingredients are combined and the reactions proceed without any further input. Batch fermentation has been used for millennia to make bread and alcoholic beverages, and it is still a common method, especially when the process is not well understood. However, it can be expensive because the fermentor must be sterilized using high pressure steam between batches. Strictly speaking, there
6930-440: The discovery of anaerobic respiration. Later, it had been defined as catabolism that forms ATP through only substrate-level phosphorylation . However, several pathways of fermentation have been discovered to form ATP through an electron transport chain and ATP synthase , also. Some sources define fermentation loosely as any large-scale biological manufacturing process. See Industrial fermentation . This definition focuses on
7029-406: The dough and may change the microbial ecosystem. The intervals between refreshments of the starter may be reduced in order to increase the rate of gas (CO 2 ) production, a process described as "acceleration." In this process, the ratio of yeasts to lactobacilli may be altered. Generally, if once-daily refreshment-intervals have not been reduced to several hours, the percentage amount of starter in
7128-445: The dough. Obtaining a satisfactory rise from sourdough takes longer than a dough leavened with baker's yeast because the yeast in a sourdough is less vigorous. In the presence of lactic acid bacteria, however, some sourdough yeasts have been observed to produce twice the gas of baker's yeast. The acidic conditions in sourdough, along with the bacteria also producing enzymes that break down proteins, result in weaker gluten and may produce
7227-1036: The early 1900s it was discovered the use of calcium chloride , ammonium sulfate , and potassium bromate halved the amount of yeast needed to raise dough. These mixtures were generally known as mineral yeast foods or yeast nutrient salts. After they became popular among bakers, one patented yeast food was analyzed by Connecticut Agricultural Experiment Station chief chemist J.P. Street who published in 1917 that it contained, " calcium sulphate , 25; ammonium chlorid, 9.7; potassium bromate, 0.3; sodium chlorid, 25; patent wheat flour, 40." They contain water conditioners, yeast conditioners, and dough conditioners. Yeast requires water, carbon sources such as starch and simple carbohydrates, nitrogen preferably as ammonium as it cannot assimilate nitrate , sulfur, phosphorus (often as inorganic phosphate), and minute quantities of vitamins and elemental mineral ions. Ammonium chloride , ammonium sulfate , or ammonium phosphate may be used as sources of nitrogen . Phosphoric acid , an acidulant ,
7326-462: The electron donor and acceptor. A common electron donor is glucose , and pyruvate is a common electron acceptor. This definition distinguishes fermentation from aerobic respiration , where oxygen is the acceptor, and types of anaerobic respiration where inorganic compound is the acceptor. Fermentation had been defined differently in the past. In 1876, Louis Pasteur defined it as "la vie sans air" (life without air). This definition came before
7425-411: The end-product is mostly lactic acid, or heterolactic fermentation , where some lactate is further metabolized to ethanol and carbon dioxide (via the phosphoketolase pathway), acetate, or other metabolic products, e.g.: If lactose is fermented (as in yogurts and cheeses), it is first converted into glucose and galactose (both six-carbon sugars with the same atomic formula): Heterolactic fermentation
7524-544: The fermentation. Investigations of wheat sourdough found that S. cerevisiae died off after two refreshment cycles. S. cerevisiae has less tolerance to acetic acid than other sourdough yeasts. Continuously maintained, stable sourdough cannot be unintentionally contaminated by S. cerevisiae. In Type II sourdoughs, baker's yeast or Saccharomyces cerevisiae is added to leaven the dough; L. pontis and Limosilactobacillus panis in association with Lactobacillus species are dominant members of type II sourdoughs. They have
7623-462: The fermentor between batches can be avoided using various open fermentation approaches that are able to resist contamination. One is to use a naturally evolved mixed culture. This is particularly favored in wastewater treatment, since mixed populations can adapt to a wide variety of wastes. Thermophilic bacteria can produce lactic acid at temperatures of around 50 °Celsius, sufficient to discourage microbial contamination; and ethanol has been produced at
7722-404: The final dough should be reduced to obtain a satisfactory rise during proof. Faster starter processes, requiring fewer refreshments, have been devised, sometimes using commercial sourdough starters as inoculants. These starters generally fall into two types. One is made from traditionally maintained and stable starter doughs, often dried, in which the ratios of microorganisms are uncertain. Another
7821-433: The gluten molecules. The addition of these agents to flour will create a stronger dough. Dehydroascorbic acid and potassium bromate are oxidants, acting on sulfhydryl groups and disulfide bonds in wheat dough, in particular oxidizing glutathione . Potassium bromate acts more directly or with fewer chemical conversion steps than ascorbic acid. Glutathione increases wheat dough's extensibility, or relaxes it, while oxidizing
7920-425: The gut that carry out fermentation, releasing products used by the host for energy. Fermentation is used at an industrial level to produce commodity chemicals, such as ethanol and lactate. In total, fermentation forms more than 50 metabolic end products with a wide range of uses. The definition of fermentation has evolved over the years. The most modern definition is catabolism where organic compounds are both
8019-411: The method used, the hydration of the starter and the final dough, the refreshment ratio, the length of the fermentation periods, ambient temperature, humidity, and elevation, all of which contribute to the microbiology of the sourdough. The starter must be fed 4 to 12 hours prior to being added to dough, by mixing flour and water to the starter. This creates an active leaven, which should grow in size and
8118-452: The most prevalent species belong to the very large and diverse genus, Lactobacillus . Lactic acid bacteria are a group comprising aerotolerant anaerobes , meaning anaerobes that can multiply in the presence of oxygen, and microaerophiles , meaning microbes that multiply at levels of oxygen lower than atmospheric. Major lactic acid bacteria in sourdough are heterofermentative (producing more than one product) organisms and convert hexoses by
8217-718: The phosphoketolase pathway to lactate, CO 2 and acetate or ethanol; heterofermentative lactic acid bacteria are usually associated with homofermentative (producing mainly one product) lactobacilli, particularly Lactobacillus and Companilactobacillus species. The most common yeast species in sourdough are Kazachstania exigua ( Saccharomyces exiguus ), Saccharomyces cerevisiae , K. exiguus and K. humilis (previously Candida milleri or Candida humilis ). Traditional sourdoughs used as sole leavening agent are referred to as Type I sourdough; examples include sourdoughs used for San Francisco Sourdough Bread, Panettone, and rye bread. Type I sourdoughs are generally firm doughs, have
8316-557: The post-mix handling characteristics of dough. Common reducing agents are: Lecithin, monoglycerides, diglycerides, and DATEM are considered emulsifiers. They disperse fat more evenly throughout the dough, helping it to trap more of the CO 2 produced by yeast. Lecithin added at a rate of 0.25-to-0.6% of the flour weight acts as a dough conditioner. Based on total weight, egg yolk contains about 9% lecithin. Monoglycerides and diglycerides replace eggs in baked goods. Emulsifiers tend to produce
8415-407: The present. For example, in the 1930s, it was discovered microorganisms could be mutated with physical and chemical treatments to be higher-yielding, faster-growing, tolerant of less oxygen, and able to use a more concentrated medium. Strain selection and hybridization developed as well, affecting most modern food fermentations. The field of fermentation has been critical to the production of
8514-519: The process of manufacturing rather than metabolic details. Fermentation is used by organisms to generate ATP energy for metabolism. One advantage is that it requires no oxygen or other external electron acceptors, and thus it can be carried when those electron acceptors are absent. A disadvantage is that it produces relatively little ATP, yielding only between 2 and 4.5 per glucose compared to 32 for aerobic respiration. Over 25% of bacteria and archaea carry out fermentation. This type of metabolism
8613-607: The production of a wide range of fermented products that are now consumed around the world. Flour treatment agent A dough conditioner , flour treatment agent , improving agent or bread improver is any ingredient or chemical added to bread dough to strengthen its texture or otherwise improve it in some way. Dough conditioners may include enzymes , yeast nutrients, mineral salts, oxidants and reductants , bleaching agents and emulsifiers . They are food additives combined with flour to improve baking functionality. Flour treatment agents are used to increase
8712-403: The production of high-value products like antibiotics and enzymes. In the 1970s and 1980s, fermentation became increasingly important in the production of bulk chemicals like ethanol, lactic acid, and citric acid. This led to the development of new fermentation techniques and the use of genetically engineered microorganisms to improve yields and reduce production costs. In the 1990s and 2000s, there
8811-430: The quality of gluten-free breads, such as by enhancing texture, aroma, and shelf life . Fermentation Fermentation is a type of redox metabolism carried out in the absence of oxygen . During fermentation, organic molecules (e.g., glucose ) are catabolized and donate electrons to other organic molecules. In the process, ATP and organic end products (e.g., lactate ) are formed. Because oxygen
8910-411: The range of about 1–10% of the lactobacilli populations or 1:10–1:100. One characteristic of a stable dough is that the heterofermentative have outcompeted homofermentative lactobacilli. F. sanfranciscensis has typically not been identified in spontaneous sourdoughs, even after multiple cycles of back-slopping; it was rapidly introduced in wheat sourdoughs, however, when plant materials were used to start
9009-893: The speed of dough rising and to improve the strength and workability of the dough. Examples of dough conditioners include ascorbic acid , distilled monoglycerides , citrate ester of monoglycerides, diglycerides , ammonium chloride , enzymes , diacetyl tartaric acid ester of monoglycerides or DATEM , potassium bromate , calcium salts such as calcium iodate , L-cystine , L-cysteine HCl, glycerol monostearate , azodicarbonamide , sodium stearoyl lactylate, sucrose palmitate or sucrose ester, polyoxyethylene sorbitan monostearate or polysorbate , soybean lecithin , and soybean lecithin enriched with lysophospholipids. Less processed dough conditioners include sprouted- or malted-grain flours, soy, milk, wheat germ, eggs, potatoes, gluten, yeast, and extra kneading. Malted, diastatic flours are not typically added by manufacturers to whole-wheat flours . In
9108-505: The starch in the flour and other carbohydrates known as pentosans . However, rye amylase remains active at higher temperatures than wheat amylase, which can cause the bread’s structure to weaken as the starches break down during baking. The lowered pH of a sourdough starter inactivates the amylases when heat alone cannot, allowing the carbohydrates to gel and set properly in the bread structure. In southern Europe, sourdough remains traditional for certain breads like panettone . However, in
9207-552: The starter through the environment, water, and flour used to create the starter. The lactic acid bacteria are a group of gram-positive bacteria capable of converting carbohydrate substrates into organic acids and producing a wide range of metabolites. Organic acids, including propionic, formic, acetic acid, and lactic acid, create an unfavorable environment for the growth of spoilage and pathogenic microorganisms. Lactic acid bacteria commonly found in sourdough include Leuconostoc , Pediococcus , Weissella and other genera. But by far,
9306-565: The use of baker's yeast as a leavening agent dates back less than 150 years". Sourdough remained the usual form of leavening down into the European Middle Ages until being replaced by barm from the beer brewing process, and after 1871 by purpose-cultured yeast. Bread made from 100% rye flour, popular in northern Europe, is typically leavened with sourdough rather than baker’s yeast, as rye lacks sufficient gluten to support yeast leavening. Instead, rye bread’s structure relies on
9405-419: The use of barm from beer making, then, after the confirmation of germ theory by Louis Pasteur , by cultured yeasts. Although sourdough bread was superseded in commercial bakeries in the 20th century, it has undergone a revival among artisan bakers and, more recently, in industrial bakeries. In countries where there is no legal definition of sourdough bread, the dough for some products named or marketed as such
9504-409: The use of commercial yeast to jump-start a culture while capturing wild yeasts, or adding grapes or milk. The preparation of sourdough begins with a pre-ferment (the "starter" or "leaven", also known as the "chief", "chef", "head", "mother" or "sponge"), a fermented mixture of flour and water, containing a colony of microorganisms including wild yeast and lactobacilli . The purpose of the starter
9603-419: Was a growing interest in the use of fermentation for the production of functional foods and nutraceuticals, which have potential health benefits beyond basic nutrition. This led to the development of new fermentation processes and the use of probiotics and other functional ingredients. Overall, the period from 1930 onward saw significant advancements in the use of fermentation for industrial purposes, leading to
9702-443: Was lampooned in an anonymous publication by Justus von Liebig and Friedrich Wöhler . The turning point came when Louis Pasteur (1822–1895), during the 1850s and 1860s, repeated Schwann's experiments and showed fermentation is initiated by living organisms in a series of investigations. In 1857, Pasteur showed lactic acid fermentation is caused by living organisms. In 1860, he demonstrated how bacteria cause souring in milk,
9801-467: Was not until the California Gold Rush in the 1850s that ethanol was first used as a fuel in the United States. Rudolf Diesel demonstrated his engine, which could run on vegetable oils and ethanol, in 1895, but the widespread use of petroleum-based diesel engines made ethanol less popular as a fuel. In the 1970s, the oil crisis reignited interest in ethanol, and Brazil became a leader in ethanol production and use. The United States began producing ethanol on
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